R.F. signal summing using non-linear optical phase conjugation

Abstract

A system for summing RF modulated optical signals. In order to compensate for performance degradation at the summing junction, the system utilizes four-wave mixing elements to provide the phase conjugates of each of the modulated RF signals. The phase conjugates of the RF modulated optical signals are summed at the summing junction. The use of the phase conjugates of the RF modulated optical signals compensates for optical phase errors known to degrade performance when summing RF modulated optical signals.

What is claimed and desired to be covered by a letters patent is as follows: 
     
       1. A system for summing RF signals modulated onto an optical carrier, the system comprising: an optical carrier source;   a plurality of RF signal sources;   a plurality of modulators for applying said plurality of RF signal sources onto a conjugate of said optical carrier source defining a plurality of modulated RF optical signals; and   a summing junction for summing said plurality of RF optical signals.   
     
     
       2. The system as recited in claim 1, wherein at least one of said plurality of modulators includes a four-wave mixing (FWM) device and means for generating pump signals. 
     
     
       3. The system as recited in claim 2, wherein said generating means includes a plurality of pump lasers. 
     
     
       4. The system as recited in claim 3, wherein said pump lasers are laser diodes. 
     
     
       5. The system as recited in claim 2, wherein said four-wave mixing device includes an optical modulator and a four-wave mixing media and said optical modulator and four-wave mixing media are formed as a single device. 
     
     
       6. A method for summing optical signals, the method comprising the steps of: (a) generating the phase conjugates of each of said optical signals defining phase conjugate signals; and   (b) summing said phase conjugate signals.   
     
     
       7. The method as recited in claim 6, wherein step (a) includes the steps of: (c) providing an optical carrier;   (d) receiving RF signals; and   (e) applying said RF signals onto a conjugate of said optical carrier defining RF modulated optical signals.   
     
     
       8. The method as recited in claim 6, wherein said phase conjugates are generated by four-wave mixing devices. 
     
     
       9. A system for summing optical signals, the system comprising: (a) means for generating the phase conjugates of said optical signals to be summed, defining phase conjugate signals; and   (b) means for summing said phase conjugate signals.   
     
     
       10. The system as recited in claim 9, wherein said generating means includes an optical carrier; means for receiving RF signals; and means for applying said RF signals onto a conjugate of said optical carrier defining RF modulated optical signal. 
     
     
       11. The system as recited in claim 10, wherein said generating means includes a four-wave mixing device. 
     
     
       12. A system for summing RF signals from a phase array antenna system having a plurality of antenna elements, the system comprising: a plurality of RF signal port for receiving RF signals from said plurality of antenna elements;   an optical carrier source for generating an optical carrier signal;   a partially reflecting mirror for transmitting said optical carrier signal and reflecting an output signal;   an optical node for splitting said optical carrier signal into a plurality of optical carrier signals and summing signals from said plurality of antenna elements;   means for applying said RF signals onto a conjugate of said optical carrier signals defining RF modulated optical signals;   means for directing said RF modulated optical signals to said optical node, where said RF optical signals are summed defining said output signal; and   means for directing said output signal to said mirror.   
     
     
       13. The system as recited in claim 12, wherein said applying means includes a four-wave mixing device.